This invention relates to an improved method employing a laser apparatus for removal of hair from patients, based upon the patients"" type of skin color, hair color and hair texture. More particularly, it relates to the method of using a laser apparatus to emit pulses in groups having defined parameters, each group consisting of a closely spaced (less than 20 ms between each pulse) sequence of pulses of coherent light energy (hereinafter xe2x80x9cparametrically defined pulse groupsxe2x80x9d), which are transmitted to the same area of the skin through an optical delivery system. In this manner, the operator can control and vary the number of laser pulses, the pulse width of each pulse, the delay between each pulse, and the power level or fluence per pulse in treating a patient depending on skin color, hair color and hair texture.
Hair removal by lasers is a new clinical field developed in the early nineties and only commercially available to patients since 1996. Lasers allow the rapid removal of large areas of hair, veins or capillaries on almost any body area, such as on the face, arms, legs, breasts, hands, stomach and the like. Laser treatment provides an unusually low discomfort level to the patient, and hair removal may last for weeks on a body area. However, all of the current lasers used for hair removal are problematic and produce unwanted side effects such as burning the skin, changes in skin pigmentation, and sometimes permanent scarring.
The currently available lasers use different approaches to hair removal, and use different laser technologies. For example, the ND:YAG laser was the first commercially available laser, but is the least effective, and does not provide permanent hair removal. The ruby laser emits a fixed wavelength of 694 nm, but has a propensity to burn the skin of the individual being treated. Because of this problem, ruby lasers cannot be used to treat olive-skinned or tanned individuals. The alexandrite laser emits a fixed wavelength of 755 nm (near the infrared spectrum), but has a propensity to burn the skin of the individual being treated, and is less effective than ruby laser treatment. Also, lasers presently being used do not consistently and reliably provide permanent hair removal, they require multiple treatments, and often burn the skin.
Pulsed flashlamps emit filtered visible light having wavelengths in the range of 550 nm and above, but have not been effective in providing permanent hair removal.
Current cutaneous lasers work by delivering energy in the form of laser light which is absorbed by the cutaneous target, heating the target and thereby causing its destruction. Different skin structures have different colors, different surface to volume configurations, and other factors which cause differential rates of heat loss. All of the hair removal lasers work by application of the principal of selective photothermoloysis, i.e. selective destruction due to heat caused by absorption of light. Laser light, which has a single wavelength, is optimally absorbed by a target which has a complementary specific color. This laser target is called a chromophore. The usual chromophore for hair removal lasers is melanin, found in high concentration in brown and black hair, and is responsible for the color of hair.
The clinical problem is that melanin is also found in the epidermis, and is responsible for native skin color and tan. Laser energy is therefore also absorbed into the epidermis. The problem of hair removal by lasers therefore is to deliver laser energy that heats the hair to a sufficient degree to cause permanent damage and hair loss, yet spare the skin of any damage. Present lasers are unable to accomplish this. For example, ruby lasers work in removing hair follicles because the wavelength of 694 nm which is emitted, is selectively absorbed by melanin and less so by other cutaneous structures, such as blood vessels. In fair skin, with little melanin, selectivity is sufficient to allow sparing of the skin and destruction of hair with even a single pulse. Alexandrite lasers perform similarly, but since their absorption by melanin is somewhat lower they seem to be less effective than ruby lasers, at least in their current forms.
The Cynosure(copyright) laser adds another approach, which they call Thermokinetic Selectivity(trademark). This means the selective destruction of the target with the same chromophore as the skin (i.e. melanin), due to less efficient heat conduction out of the hair (as compared with the epidermis). This less efficient heat conduction is due to a variety of factors, the main one being the unfavorably large volume to surface area of the hair. The Cynosure(copyright) laser, like the ruby lasers, uses a single pulse, but the pulse used by this alexandrite laser is longer (5-20 ms). This longer pulse allows more gradual accumulation of heat by the skin, so the heat has time to dissipate (cool) and to prevent burning of the skin. This technique improves safety, but the technique is not able to deliver enough heat to provide permanent hair loss, and some burns still occur.
The use of medical lasers to produce permanent hair removal in patients with hair of all colors, and skin of all colors, has, up to this time, been impossible to achieve with current technology. While promising, the currently-used lasers have all been unable to treat patients with dark skin. In addition, even in Caucasian patients, the currently-used lasers have burned many patients, leading to prolonged changes in skin color and even, in some cases, to permanent scarring. Hair loss, although usually prolonged, has not been permanent for the majority of patients.
Nevertheless, the use of monochromatic (laser) light in the range of 694 to 900 nm still appears to be the most effective way to achieve long-term hair removal. To achieve predictable permanency we need to achieve higher temperatures in the hair without heating the epidermis to the point where it is burned. The single pulse techniques described above are inadequate to accomplish this.
There remains a need for an improved method which will supply a series of laser energy pulses with short time delays between pulses to heat a hair follicle sufficiently to cause permanent damage to that hair follicle, and yet spare the skin from burning, thus providing a safe and permanent method of hair removal for use on patients with different types of skin color, hair color and hair texture.
A new method of treatment has been developed that has the following major advantages: 1) increased efficacy, causing greater hair loss and true permanent hair removal; 2) increased safety, with burning of the skin eliminated, so that treatment has no side effects; 3) increased speed of treatment, nearly by a factor of two; 4) cooling of the skin; and 5) it allows the use of laser hair removal for patients with all skin and hair colors, thereby greatly increasing the range of people who can be treated with this technology.
Laser apparatus and methods for hair removal having various structures have been disclosed in the prior art. For example, U.S. Pat. Nos. 5,630,811 and 5,658,323 to Miller disclose a method and apparatus for dermatology treatments for lesions and hair removal using a modified laser device. The specific target for the laser radiation is the melanin within the hair shaft and within the melanocytes lining of the follicular duct. Pulse width is controlled to provide a direct thermal effect from a single pulse.
U.S. Pat. No. 5,647,866 to Zaias discloses a method of hair depilation through the application of pulsed laser energy having a wavelength readily absorbed by hemoglobin. The process of selective photothermoloysis is used by the laser to focus on a particular region in the epidermis to be irradiated. The pulse duration or time period (30 to 40 nanoseconds) is shorter than the thermal relaxation time for melanin in hair.
U.S. Pat. No. 5,683,380 to Eckhouse discloses a method and apparatus for removing hair (depilation) using a single high intensity pulsed flashlamp (not a laser) which emits a broad spectrum of pulsed incoherent light that is polychromatic. Because of the broad spectrum of wavelengths emitted by the flashlamp, only part of the light energy is absorbed by the hair, making it inefficient for permanent hair removal, although it does provide temporary hair loss.
U.S. Pat. No. 5,595,568 to Anderson et al discloses a method for permanent hair removal from a skin region of a patient using a single laser with a single pulse. This prior art patent does not teach or disclose defined pulse groups from a laser apparatus as in the present invention.
U.S. Pat. No. 5,735,844 by Anderson discloses a method for hair removal using optical pulses. The method involves using a cooled contact applicator and a single pulse. Unlike the present invention there is no disclosure of defined pulse groups (multipulsing) to the same location, with each group consisting of a closely spaced sequence of pulses, delivered to the same area of the skin (multipulsing). Nor is there any mention of a method to adjust the parameters of a defined pulse group according to skin color, hair color, and hair diameter in order to achieve safe and effective permanent hair removal. A single pulse method, as disclosed by Anderson, has a propensity to burn the skin and is unable to deliver the amount of energy that can be safely delivered by the present invention. Additionally, the present invention does not require a cooled contact applicator which is an integral part of the method disclosed by Anderson.
U.S. Pat. No. 5,752,948 to Tankovich discloses a laser hair removal method utilizing a Nd:Yag laser operating at 1.06 micron wavelength and with a pulse duration of 10 to 50 nanoseconds. This pulse duration is too short to be effective, and much shorter than that disclosed in the present invention. A pulse duration of 1.2 ms or greater is necessary to achieve permanent damage to the hair germinative apparatus. The use of Nd:Yag lasers with this short pulse duration has failed to accomplish long-term hair removal and has largely been abandoned by the medical community.
U.S. Pat. No. 5,814,040 to Nelson et al discloses a method and apparatus for dynamic cooling of biological tissues for thermal medicated surgery. The method employs dynamic cooling of the epidermal tissue with a cryogen spray. However, the cooling is applied before the laser pulse and no intra-pulse cooling occurs.
U.S. Pat. No. 5,879,346 to Waldman et al discloses a treatment method of hair removal by selective photothermolysis with an Alexandrite laser. However, there is no use of multiple pulses as in the present invention.
U.S. Pat. No. 5,885,273 to Eckhouse et al discloses a method for depilation using pulsed electromagnetic radiation. This method employs the use of a flashlamp (or incoherent light) wherein the present invention uses a laser apparatus.
U.S. Pat. No. 5,871,479 to Furomoto et al discloses a method and apparatus for hair removal using an Alexandrite laser system. However, this method has no mention of treatment for light and dark skin patients, nor any mention of cooling the patient""s skin during treatment.
None of these prior art patents disclose the particular structure of the present invention or a method of using a laser apparatus to emit a closely spaced pulse sequence (multipulsing) with proper parameters for safe and permanent hair removal for use on patients with different skin colors, hair colors and hair textures.
Accordingly, it is an object of the present invention to provide an improved laser apparatus and method which supplies a defined pulse group of laser energy with short delays between the pulses from a laser apparatus to heat a hair follicle and hair follicle shaft to cause permanent damage to that hair follicle and shaft, and yet spare the skin from burning, thus providing a safe and permanent method of hair removal for patients with different skin colors, hair colors and hair textures.
Another object of the present invention is to provide an improved laser apparatus, controlled by a sequence control device, and a fiber optic cable which sequentially emits a defined pulse group having pulses of coherent light energy from the fiber optic cable for permanently removing a plurality of hair follicles from the skin area of a patient.
Another object of the present invention is to provide an improved laser apparatus having a handpiece for ease of use by the operator in directing the defined pulse group of laser pulses at the skin to rapidly remove large areas of hair on almost any body area, such as on the face, hands, arms, legs, breasts, stomach and the like, where such treatment provides a low discomfort level to the patient.
Another object of the present invention is to provide a laser apparatus and a sequence control device for emitting laser energy through an optical delivery system which delivers a defined pulse group of sequential pulses from the laser apparatus.
Another object of the present invention is to provide an improved method for adjusting the defined pulse group with regard to the numbers of pulses, the pulse width, the time delay between pulses, and the energy level of each pulse, to customize treatment and the energy delivered to the spot being treated according to skin color, hair color, hair texture (diameter) and the anatomic site being treated.
Another object of the present invention is to provide safe and permanent hair removal in a wider range of patients having different skin colors, such as a light skin color for Caucasians, a medium skin color for Hispanics, American Indians, Eastern Mediterranean-types, and a dark skin color for Africans and Afro-Americans.
Another object of the present invention is to provide safe and permanent hair removal in a wider range of patients having different hair colors and different hair textures. Such hair colors include gray and white hair; blond hair; red hair; light, medium and dark brown hair; and black hair; and having hair texture (diameter) of fine or coarse hair. Generally, the present invention will accommodate all persons having hair which is darker than their skin.
Another object of the present invention is to provide a delay between laser pulses which is much shorter than the thermal relaxation time of the hair being treated, so the hair does not cool off between pulses.
Another object of the present invention is to provide a method and laser apparatus wherein the delay between laser pulses is so short that less energy has to be transmitted to the hair to cause permanent hair loss.
Another object of the present invention is to provide an improved laser apparatus and method that is easy to use, and the laser apparatus is durable, light-weight and easily maintained.
Another object of the present invention is to provide an improved laser apparatus that provides a wider beam area (spot size on the skin) by utilizing a laser apparatus and a sequence control device for delivering enough laser energy to each spot allowing the spot size to be made larger for faster treatment.
Another object of the parametrically defined pulse group (PDPG) of the present invention is that it provides for laser hair removal to be successful in clinical situations where it previously was impossible; and it allows for both greater efficacy and greater safety by taking advantage of thermodynamic differences between hair follicles and epidermis when both are simultaneously irradiated by the laser apparatus.
A further object of the present invention is to provide an improved laser apparatus that is simple to manufacture and assemble in an economical manner, and is cost effective for the user.
In accordance with the present invention, there is provided an improved method employing a laser apparatus and a sequence control device to emit groups of pulses, each pulse group consisting of a closely spaced sequence of pulses for permanently, safely and quickly removing a plurality of hair follicles from the skin of a patient, based upon the patients"" type of skin color, hair color and hair texture. These include patients having light, medium and dark skin color, and with hair colors that include light and medium brown hair, and black hair; and having fine or coarse hair texture.
A method is provided of removing hair from the skin of a patient using a laser apparatus capable of producing an emission of laser energy in the form of a group of pulses having defined parameters, being a defined pulse group, and using an optical delivery system, which includes the steps of controlling the laser apparatus in each emission of laser energy to emit a defined pulse group of 2 to 20 pulses of coherent light energy; transmitting the defined pulse group of pulses of coherent light energy through an optical delivery system to the same spot on the skin of the patient; irradiating the same spot on the skin containing the hair to be removed with the defined pulse group of coherent light energy transmitted through the optical delivery system from the laser apparatus; controlling the laser apparatus in each emission of laser energy to emit the defined pulse group through the optical delivery system, the defined pulse group having 2 to 15 pulses at a wavelength in the range of 550 to 1200 nm, each pulse at a power level in the range of 2 to 35 Joules/cm2 per pulse, each pulse having a pulse duration in the range of 1.2 to 22 milliseconds per pulse, each pulse having a beam diameter on the treatment area in the range of 4 to 50 millimeters, the defined pulse group having a total fluence in the range of 4 to 100 Joules/cm2, and a repetition rate of the laser apparatus between successive defined pulse groups being 500 to 2000 milliseconds; and cooling the skin during at least one delay between pulses of the defined pulse group, wherein the at least one delay between pulses is longer to accommodate the cooling step, and wherein the step of cooling is performed by spraying cryogen on the patient""s skin. Additional cooling may also be performed before and/or after the defined pulse group.
Alternatively, an optional method for cooling the skin is using a thermoelectric device within the laser handpiece that includes a sapphire crystal which engages the skin area of the patient. The cooling temperature of the skin when using the thermoelectric device is in the temperature range of xe2x88x9230xc2x0 C. to 0xc2x0 C. having a pulsing range of xc2xc second to 2 seconds, with a preferable pulse being 2 seconds. The cooling may be performed before, during and/or after the defined pulse group.
The new technology requires that a series of relatively low energy laser pulses be delivered in rapid succession with short delays between pulses to exactly the same area of the skin, so that the hair does not have time to dissipate the heat between pulses. Relatively low energy per pulse is delivered to the hair germinative apparatus using a series of short pulses from the laser apparatus, with the pulses repeated at short intervals so the hair does not have time to dissipate the heat energy between pulses. For most patients, this means five or less low-energy (1xc2xd to 25 Joules/cm2), medium duration (2 to 6 milliseconds) pulses, separated by short delays of less than 20 milliseconds, each with a large (e.g. 10 millimeters or greater) spot size. None of the currently-produced lasers are able to produce these results. The short delay between pulses is shorter than the thermal relaxation time of the hair being treated, so the hair does not cool off between the pulses. Selective cooling of the epidermis, while not always necessary with the present invention, will be helpful to prevent epidermal damage and will allow greater laser energy to be delivered to the skin and hair. The method of epidermal cooling will impact upon the epidermal response to any given pulse sequence. Epidermal cooling may be passive, or may be done actively. Active epidermal cooling can be accomplished with ice, cold, clear ultrasound gel, or with a cooled contact applicator as disclosed by Chess in U.S. Pat. No. 5,057,104, with a thermoelectric applicator, or with cryogen spray. Individual pulse sequence parameters, particularly the delay between pulses and the total fluence delivered, will vary according to the method and the amount of epidermal cooling applied prior to, and/or during, and/or after the exposure of the skin to the laser pulse sequence.
For example, short pulse duration lasers (with a pulse duration measured in nanoseconds) can repeat rapidly, but these are too short and are not suitable for optimal hair removal. A temperature of 70 degree xc2x0 C. sustained for 1 ms or longer at the hair germinative apparatus is necessary to accomplish permanent hair removal. This requires a laser with a pulse duration of 1.2 ms or longer. All of the new hair removal lasers (ruby, alexandrite, diode) are long pulse lasers. Most of these recycle every 1000 milliseconds, with the fastest recycling every 100 milliseconds. The repetition rate that is necessary, however, must be a delay between pulses of less than 20 milliseconds. The new laser apparatus of the present invention is able to accomplish this new method.